Merge #1934

1934: Parse Path and AttrInput in Attr r=matklad a=uHOOCCOOHu

[Syntax reference](https://doc.rust-lang.org/reference/attributes.html#attributes)

Co-authored-by: uHOOCCOOHu <[email protected]>

1 files changed, 17 insertions, 2 deletions

diff --git a/crates/ra_parser/src/grammar/attributes.rs b/crates/ra_parser/src/grammar/attributes.rs
index 1cfd301b5..63ca9ca32 100644
--- a/crates/ra_parser/src/grammar/attributes.rs
+++ b/crates/ra_parser/src/grammar/attributes.rs
@@ -22,8 +22,23 @@ fn attribute(p: &mut Parser, inner: bool) {
         p.bump(T![!]);
     }
 
-    if p.at(T!['[']) {
-        items::token_tree(p);
+    if p.eat(T!['[']) {
+        paths::use_path(p);
+
+        match p.current() {
+            T![=] => {
+                p.bump(T![=]);
+                if expressions::literal(p).is_none() {
+                    p.error("expected literal");
+                }
+            }
+            T!['('] | T!['['] | T!['{'] => items::token_tree(p),
+            _ => {}
+        }
+
+        if !p.eat(T![']']) {
+            p.error("expected `]`");
+        }
     } else {
         p.error("expected `[`");
     }